Find and tap on the Pinterest application, which has a red and white icon with a white "P" inside of a red circle

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This takes us to our main screen, but it might take us to the home screen where we have to sign in. If we're not signed in, we can refer to the article on how to sign in using Pinterest on the iPhone 6.

Scroll and choose the board to pin it to, in this example we will choose the new secret board "Flowers"

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As we can see, the board is empty and also has a small padlock icon on the right side to indicate that it is private. A notification will appear at the bottom to tell us what board we have pinned it to.